Bulldozer

ABSTRACT

A bulldozer has a protective structure. The protective structure includes a left pillar portion, a right pillar portion, and a beam portion. The left pillar portion is disposed to the left of a cab and extends in the up-down direction. The right pillar portion is disposed to the right of the cab and extends in the up-down direction. The beam portion is disposed above the cab and couples the left pillar portion and the right pillar portion. A first camera is attached to the left pillar portion and is disposed so that a first optical axis faces forward and downward. A second camera is attached to the right pillar portion and is disposed so that a second optical axis faces forward and downward.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National stage application of InternationalApplication No. PCT/JP2016/076634, filed on Sep. 9, 2016.

BACKGROUND

Field of the Invention

The present invention relates to a bulldozer.

Background Information

A technique is known for capturing images of the surroundings of abulldozer with a camera attached to the bulldozer and displaying theimages taken by the camera on a display (“Remote Control Robot “Robo Q”for Bulldozer” [online], Ministry of Land, Infrastructure and Transport(Japan), Regional Development Bureau of Kyushu Region, Kyushu TechnicalOffice. Two cameras are attached to the roof of the cab of the bulldozerand the cameras capture images in front and to the rear of the bulldozerin this technique.

SUMMARY

In order to know the progress of work by the blade of a bulldozer, it ispreferable to obtain images near the lower edge on the right and left ofthe blade. Moreover, in order to realize the traveling state of abulldozer, it is preferable to obtain images of the rotation conditionsof the crawler belts. In particular, if the conditions near the loweredge on the right and left of the blade and the rotation conditions ofthe crawler belts can be displayed on the same screen, the progress ofwork and the traveling state can be easily understood.

However, the right and left lower edges of the blade and the right andleft crawler belts are positioned to the outside of the cab in thevehicle width direction. As a result, it is difficult to capture imagesof the right and left lower edges of the blade and the right and leftcrawler belts on both sides at the same time while capturing images ofthe blade in the front with a camera attached to the roof as in theabove-mentioned technique.

An object of the present invention is to easily understand the progressof work and the traveling state with a camera attached to a bulldozer.

A bulldozer according to a first aspect includes a vehicle body, ablade, a left crawler belt, a right crawler belt, a protectivestructure, a first camera, and a second camera. The vehicle bodyincludes a cab. The blade is disposed in front of the vehicle body. Theleft crawler belt is disposed to the left of the vehicle body. The rightcrawler belt is disposed to the right of the vehicle body. Theprotective structure includes a left pillar portion, a right pillarportion, and a beam portion. The left pillar portion is disposed to theleft of the cab and extends in the up-down direction. The right pillarportion is disposed to the right of the cab and extends in the up-downdirection. The beam portion is disposed above the cab and couples theleft pillar portion and the right pillar portion. A first camera isattached to the left pillar portion and is disposed so that the opticalaxis faces forward and downward. A second camera is attached to theright pillar portion and is disposed so that the optical axis facesforward and downward.

The first camera in the bulldozer according to the present aspect isattached to the left pillar portion positioned further to the left thanthe cab. The second camera is attached to the right pillar portionpositioned further to the right than the cab. As a result, the firstcamera and the second camera can be positioned to the outside in theleft-right direction in comparison to when the first camera and thesecond camera are attached to the roof of the cab. As a result, imagesin the vicinity of the left lower edge of the blade and the rotatingconditions of the left crawler belt as well as the front of thebulldozer can be easily captured by the first camera. Moreover, imagesin the vicinity of the right lower edge of the blade and the rotatingconditions of the right crawler belt as well as the front of thebulldozer can be easily captured by the second camera. Therefore, theprogress of work and the traveling state can be easily understood fromthe images captured by the first camera and the second camera.

A bulldozer body according to a second aspect includes a vehicle body, aleft crawler belt, a right crawler belt, a protective structure, a firstcamera, and a second camera. The vehicle body includes a cab and anengine compartment disposed in front of the cab. The left crawler beltis disposed to the left of the vehicle body. The right crawler belt isdisposed to the right of the vehicle body. The protective structureincludes a left pillar portion, a right pillar portion, and a beamportion. The left pillar portion is disposed to the left of the cab andextends in the up-down direction. The right pillar portion is disposedto the right of the cab and extends in the up-down direction. The beamportion is disposed above the cab and connects the left pillar portionand the right pillar portion. The first camera is attached to the leftpillar portion and is disposed so that the optical axis faces forwardand downward. The second camera is attached to the right pillar portionand is disposed so that the optical axis faces forward and downward.

The progress of work and the traveling state can be easily understoodfrom the images captured by the first camera and the second camera inthe bulldozer body according to the present aspect.

According to the present invention, the progress of work and thetraveling state can be easily understood with a camera attached to abulldozer.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a bulldozer according to the presentexemplary embodiment.

FIG. 2 is a side view of the bulldozer.

FIG. 3 is a plan view of the bulldozer.

FIG. 4 is a block diagram illustrating a control system of thebulldozer.

FIG. 5 is a front view of the bulldozer.

FIG. 6 is an enlarged perspective view of the left front camera and thesurroundings thereof.

FIG. 7 is an enlarged side view of the left front camera and thesurroundings thereof.

FIG. 8 illustrates an example of an image displayed on a display.

FIG. 9 is a side view illustrating the disposition of the left frontcamera according to another exemplary embodiment.

FIG. 10 is a block diagram illustrating a control system of thebulldozer according to still another exemplary embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following is a description of a bulldozer according to the presentexemplary embodiment with reference to the drawings. FIG. 1 is aperspective view of a bulldozer 1 according to the present exemplaryembodiment. FIG. 2 is a side view of the bulldozer 1. FIG. 3 is a planview of the bulldozer 1. As illustrated in FIGS. 1 to 3, the bulldozer 1includes a vehicle body 2, left and right crawler belts 10 a and 10 b, ablade 3, and a ripper device 4.

The vehicle body 2 includes an engine compartment 5 and a cab 6. Theengine compartment 5 is provided in the front portion of the vehiclebody 2. The engine compartment 5 is disposed to the rear of the blade 3.An engine 21 (see FIG. 4) is disposed inside the engine compartment 5.The cab 6 is disposed to the rear of the engine compartment 5.

The left and right crawler belts 10 a and 10 b are devices for causingthe bulldozer 1 to travel. The left crawler belt 10 a is disposed to theleft of the vehicle body 2. The right crawler belt 10 b is disposed tothe right of the vehicle body 2. The left and right crawler belts 10 aand 10 b are driven by a driving power from the engine 21, whereby thebulldozer 1 travels.

The blade 3 is disposed in front of the vehicle body 2. The blade 3 issupported by a left arm 7 a and a right arm 7 b. The left arm 7 a isattached to the left side portion of the vehicle body 2. The right arm 7b is attached to the right side portion of the vehicle body 2.

The bulldozer 1 includes left and right lift cylinders 8 a and 8 b andleft and right tilt cylinders 9 a and 9 b. The left and right liftcylinders 8 a and 8 b and the left and right tilt cylinders 9 a and 9 bare hydraulic cylinders and extend and contract due to hydraulic fluiddischarged from a hydraulic pump 22 (see FIG. 4). The left and rightlift cylinders 8 a and 8 b are connected to the blade 3 and the vehiclebody 2. The left and right lift cylinders 8 a and 8 b move the blade 3up and down. While two lift cylinders are provided in the presentexemplary embodiment, the number of lift cylinders may be one.

The left tilt cylinder 9 a is connected to the blade 3 and the left arm7 a. The right tilt cylinder 9 b is connected to the blade 3 and theright arm 7 b. The left and right tilt cylinders 9 a and 9 b move theblade 3 to the left and right.

The ripper device 4 is disposed to the rear of the vehicle body 2. Theripper device 4 is attached to the rear portion of the vehicle body 2.The ripper device 4 includes hydraulic cylinders 11 a-11 d and a shank12. The hydraulic cylinders 11 a-11 d are driven by hydraulic fluid fromthe hydraulic pump 22 and consequently move the shank 12 up and down.The ripper device 4 may be omitted.

The bulldozer 1 includes a roll over protective structure (ROPS) 13. TheROPS 13 is erected on the upper surface of the vehicle body 2 and isdisposed so as to surround the cab 6 from the left and right sides andfrom above. The ROPS 13 includes a left pillar portion 13 a, a rightpillar portion 13 b, and a beam portion 13 c. The left pillar portion 13a is disposed to the left of the cab 6 and extends in the up-downdirection. The right pillar portion 13 b is disposed to the right of thecab 6 and extends in the up-down direction. The beam portion 13 c isdisposed above the cab 6 and connects the left pillar portion 13 a andthe right pillar portion 13 b. The ROPS 13 is a gate-like frame thatcovers the cab in the left and right directions.

A plurality of left indicator lamps 14 and a plurality of rightindicator lamps 15 are attached to the ROPS 13. The indicator lamps 14and 15 are rotating lamps. However, the left indicator lamps 14 and theright indicator lamps 15 may be a type of indicator lamp other than arotating lamp. The plurality of left indicator lamps 14 are attached tothe left pillar portion 13 a and are disposed in the up-down direction.As illustrated in FIG. 6, the plurality of left indicator lamps 14 areattached to the left pillar portion 13 a via a first bracket 53. Thefirst bracket 53 protrudes upward from the ROPS 13.

The plurality of right indicator lamps 15 are attached to the rightpillar portion 13 b and are disposed in the up-down direction. Theplurality of right indicator lamps 15 are attached to the right pillarportion 13 b via a second bracket 54. The second bracket 54 protrudesupward from the ROPS 13.

FIG. 4 is a block diagram illustrating a control system of the bulldozer1. As illustrated in FIG. 4, the bulldozer 1 includes the engine 21, thehydraulic pump 22, and a pump displacement control device 23. Thehydraulic pump 22 is driven by the engine 21 to discharge hydraulicfluid. The hydraulic pump 22 is a variable displacement pump. The pumpdisplacement control device 23 controls the discharge displacement ofthe hydraulic pump 22. For example, the pump displacement control device23 includes a spool coupled to a swash plate or an inclined shaft of thehydraulic pump 22. The discharge displacement of the hydraulic pump 22is changed due to the spool of the pump displacement control device 23being driven.

The bulldozer 1 includes a work implement control valve 24 and ahydraulic actuator 25. The hydraulic actuator 25 is driven by hydraulicfluid discharged from the hydraulic pump 22. The hydraulic actuator 25includes the above-mentioned left and right lift cylinders 8 a and 8 band the left and right tilt cylinders 9 a and 9 b. Moreover, thehydraulic actuator 25 includes the hydraulic cylinders 11 a-11 d of theripper device 4. The work implement control valve 24 controls the supplyand exhaust of the hydraulic fluid to and from the hydraulic actuator25.

The bulldozer 1 includes a power transmission device 26 and a clutchcontrol valve 27. The power transmission device 26 includes, forexample, a transmission and a torque converter. The clutch control valve27 controls the switching of a speed change clutch, a forward/reverseclutch, and a steering clutch and the like included in the powertransmission device 26.

The bulldozer 1 according to the present exemplary embodiment is avehicle that can be operated remotely. As illustrated in FIG. 4, thebulldozer 1 includes an on-board controller 28 and a communicationdevice 29. The communication device 29 is connected to an antennamounted on the vehicle body 2. The communication device 29 carries outcommunication wirelessly with a communication device 31 of a remoteoperating device 30. For example, the remote operating device 30 isdisposed in a management center away from the work site where thebulldozer 1 is being used. Alternatively, the remote operating device 30may be portable and may be disposed at the work site.

The on-board controller 28 is configured with a computation device, suchas a CPU, and a memory, such as a RAM or a ROM, or a storage device,such as a hard disk. The on-board controller 28 is programmed to controlthe bulldozer 1 on the basis of operation signals from the remoteoperating device 30.

The remote operating device 30 includes a remote controller 32 and anoperating member 33. The remote controller 32 is configured with acomputation device, such as a CPU, and a memory, such as a RAM or a ROM,or a storage device, such as a hard disk.

The operating member 33 is operated by an operator. For example, theoperating member 33 includes a deceleration operating member foradjusting the output of the engine 21. The operating member 33 includesa blade operating member for operating the blade 3. The operating member33 includes a ripper operating member for operating the ripper device 4.The operating member 33 includes a steering operating member forchanging the traveling direction of the bulldozer 1 to the right andleft. The deceleration operating member, the blade operating member, theripper operating member, and the steering operating member may be apedal, a lever, a wheel, a button, or a switch and the like.

The remote controller 32 transmits operation signals which indicate anoperation by the operating member 33 to the on-board controller 28 ofthe bulldozer 1 via the communication devices 31 and 29. The on-boardcontroller 28 controls the above-mentioned devices and the controlvalves in response to the received operation signals. For example, theon-board controller 28 controls the engine 21 in response to theoperation of the deceleration operating member. As a result, the enginerotation speed is controlled. The on-board controller 28 controls thework implement control valve 24 in response to the operation of theblade operating member or the ripper operating member. As a result, theactions of the blade 3 or the ripper device 4 are controlled.

The bulldozer 1 includes a plurality of cameras 41-46 for capturingimages of the surroundings of the bulldozer 1. The plurality of cameras41-46 include a middle front camera 41, a rear camera 42, a left sidecamera 43 (third camera), a right side camera 44 (fourth camera), a leftfront camera 45 (first camera), and a right front camera 46 (secondcamera).

The middle front camera 41 captures images in front of the bulldozer 1.As illustrated in FIG. 1, the middle front camera 41 is attached to thefront portion of the upper surface of the roof of the cab 6. The middlefront camera 41 is disposed in the middle in the vehicle width directionon the upper surface of the roof of the cab 6. The rear camera 42captures images to the rear of the bulldozer 1. The rear camera 42 isattached to the rear portion of the upper surface of the roof of the cab6. The rear camera 42 is disposed in the middle in the vehicle widthdirection on the upper surface of the roof of the cab 6. As illustratedin FIG. 3, an optical axis Ax1 of the middle front camera 41 extendstoward the front as seen in the plan view of the vehicle. An opticalaxis Ax2 of the rear camera 42 extends to the rear as seen in the planview of the vehicle.

The left side camera 43 captures images to the left of the bulldozer 1.The left side camera 43 is attached to the left pillar portion 13 a. Asillustrated in FIG. 7, the left side camera 43 is attached to the leftpillar portion 13 a via a left bracket 51. The left side camera 43 isdisposed further to the left than the left pillar portion 13 a. Asillustrated in FIG. 2, the left side camera 43 overlaps the left pillarportion 13 a as seen in a side view of the vehicle. The left side camera43 is disposed below the plurality of left indicator lamps 14.Specifically, the left side camera 43 is disposed below the lamppositioned furthest to the bottom among the plurality of left indicatorlamps 14. However, the left side camera 43 may be disposed among theplurality of left indicator lamps 14. Alternatively, the left sidecamera 43 may be disposed above the plurality of left indicator lamps14.

The right side camera 44 captures images to the right of the bulldozer1. As illustrated in FIG. 6, the right side camera 44 is attached to theright pillar portion 13 b. The right side camera 44 is attached to theright pillar portion 13 b via a right bracket 52. The right side camera44 is disposed in approximately left-right symmetry with the left sidecamera 43.

An optical axis Ax3 of the left side camera 43 extends to the left asseen in a plan view of the vehicle. An optical axis Ax4 of the rightside camera 44 extends to the right as seen in a plan view of thevehicle. FIG. 5 is a front view of the bulldozer 1. As illustrated inFIG. 5, the optical axis Ax3 of the left side camera 43 is inclined tothe left and downward. The optical axis Ax4 of the right side camera 44is inclined to the right and downward. The left front camera 45 and theright front camera 46 are omitted from the drawing in FIG. 5.

The left front camera 45 captures images in the left front direction ofthe bulldozer 1 including the left edge portion of the blade 3. FIG. 6is an enlarged perspective view illustrating the left front camera 45and the surroundings thereof. FIG. 7 is an enlarged side viewillustrating the left front camera 45 and the surroundings thereof. Asillustrated in FIGS. 6 and 7, the left front camera 45 is attached tothe left pillar portion 13 a. The left side camera 43 is attached to theleft pillar portion 13 a via the left bracket 51. The left front camera45 is disposed further to the left than the left pillar portion 13 a.The left front camera 45 is disposed further to the front than the leftpillar portion 13 a. The left front camera 45 is disposed further to thefront than the plurality of left indicator lamps 14. The left frontcamera 45 is disposed further to the front than the left side camera 43.

The left front camera 45 is disposed at the same height as the left sidecamera 43. However, the left front camera 45 may be disposed at a heightthat is different from that of the left side camera 43. The left frontcamera 45 is disposed higher than the upper edge of a window of the cab6. However, the left front camera 45 may be disposed in a position at orbelow the upper edge of the window of the cab 6.

As illustrated in FIG. 3, the left front camera 45 overlaps the leftcrawler belt 10 a as seen in the plan view of the bulldozer 1. The leftfront camera 45 is disposed further to the left than the left liftcylinder 8 a. The left front camera 45 is disposed further to the leftthan the left side surface of the engine compartment 5. The left frontcamera 45 is disposed further to the right than the left arm 7 a. Theleft front camera 45 is disposed further to the right than the left edgeportion of the blade 3.

An optical axis Ax5 of the left front camera 45 extends toward the frontas seen in the plan view of the bulldozer 1. However, the optical axisAx5 of the left front camera 45 may be inclined to the left or rightwith respect to the straight forward direction as seen in the plan viewof the bulldozer 1. In FIG. 3, the lines Va1-Va2 indicate the range ofvision in the left-right direction of the left front camera 45. Therange of vision Va1-Va2 of the left front camera 45 includes the leftside edge of the blade 3 as seen in the plan view of the bulldozer 1.The range of vision Va1-Va2 of the left front camera 45 includes theleft side surface of the engine compartment 5 as seen in the plan viewof the bulldozer 1.

As illustrated in FIG. 2, the optical axis Ax5 of the left front camera45 is inclined toward the front and downward as seen in the side view ofthe bulldozer 1. In FIG. 2, the lines Va3-Va4 indicate the range ofvision in the up-down direction of the left front camera 45. The rangeof vision Va3-Va4 of the left front camera 45 includes the upper edge ofthe blade 3 as seen in the side view of the bulldozer 1. The range ofvision Va3-Va4 of the left front camera 45 includes the front edge ofthe left crawler belt 10 a as seen in the side view of the bulldozer 1.A first virtual straight line L1 connecting the view point of the leftfront camera 45 and the lower edge of the back surface of the blade 3does not overlap with the left crawler belt 10 a as seen in the sideview of the bulldozer 1. A second virtual straight line L2 passingthrough the view point of the left front camera 45 and bordering theleft crawler belt 10 a intersects the ground surface G further towardthe rear than the first virtual straight line L1. Therefore, images ofthe portion between an intersection P1 of the first virtual straightline L1 and the ground surface C, and an intersection P2 of the secondvirtual straight line L2 and the ground surface G can be captured by theleft front camera 45 as a gap between the lower edge of the blade 3 andthe left crawler belt 10 a.

The right front camera 46 captures images in the right front directionof the bulldozer 1 including the right edge portion of the blade 3. Asillustrated in FIG. 1, the right front camera 46 is attached to theright pillar portion 13 b. The right front camera 46 is disposed furtherto the right than the right pillar portion 13 b. The right front camera46 is disposed further to the front than the right pillar portion 13 b.The right front camera 46 is disposed further to the front than theplurality of right indicator lamps 15. The right front camera 46 isdisposed further to the front than the right side camera 44. The rightfront camera 46 is disposed at the same height as the right side camera44.

As illustrated in FIG. 3, the right front camera 46 overlaps the rightcrawler belt 10 b as seen in the plan view of the bulldozer 1. The rightfront camera 46 is disposed further to the right than the right liftcylinder 8 b. In FIG. 3, the lines Vb1-Vb2 indicate the range of visionin the left-right direction of the right front camera 46. The rightfront camera 46 is disposed in approximately left-right symmetry withthe left front camera 45. Therefore, the right front camera 46 isdisposed so as to be able to capture images of the gap between the loweredge of the blade 3 and the right crawler belt 10 b in the same way asthe left front camera 45.

As illustrated in FIG. 4, the remote operating device 30 includes adisplay 34. The display 34 is a device such as a CRT, and LCD, or anOELD. However, the display 34 is not limited to the aforementioneddevices and may be another type of display.

The on-board controller 28 obtains image data captured by the pluralityof cameras 41-46. The on-board controller 28 transmits the image data tothe remote controller 32 via the communication devices 29 and 31. Theremote controller 32 is programmed to display images showing thesurroundings of the bulldozer 1 on the display 34 on the basis of theimage data from the plurality of cameras 41-46. The remote controller 32receives the image data captured by the plurality of cameras 41-46 inreal time and can display the image data as a moving image on thedisplay 34.

FIG. 8 is a view of images Ima and Imb captured by the left front camera45 and the right front camera 46 and displayed on the display 34. Theremote controller 32 respectively arranges the image Ima captured by theleft front camera 45 and the image Imb captured by the right frontcamera 46 on the left and right and displays the images on the samescreen of the display 34.

As illustrated in FIG. 8, the image Ima captured by the left frontcamera 45 includes a portion of an upper edge 3 a, a portion of a leftside edge 3 b, and a portion of a lower edge 3 c of the blade 3. Theimage Ima captured by the left front camera 45 includes the frontportion of the left crawler belt 10 a and the left side surface 2 a ofthe vehicle body 2. The image Ima captured by the left front camera 45includes a gap between the lower edge 3 c of the blade 3 and the frontedge of the left crawler belt 10 a. Therefore, the image Ima captured bythe left front camera 45 includes the ground surface Ga between theblade 3 and the left crawler belt 10 a.

The image Imb captured by the right front camera 46 includes a portionof the upper edge 3 a, a portion of a right side edge 3 d, and a portionof a lower edge 3 c of the blade 3. The image Imb captured by the rightfront camera 46 includes the front portion of the right crawler belt 10b and the right side surface 2 b of the vehicle body 2. The image Imbcaptured by the right front camera 46 includes the gap between the loweredge 3 c of the blade 3 and the front edge of the right crawler belt 10b. Therefore, the image Imb captured by the right front camera 46includes the ground surface Gb between the blade 3 and the right crawlerbelt 10 b.

The left front camera 45 is attached to the left pillar portion 13 a ata position further to the left than the cab 6 in the bulldozer 1according to the present exemplary embodiment as discussed above. Theright front camera 46 is attached to the right pillar portion 13 bpositioned further to the right than the cab 6. As a result, the leftfront camera 45 and the right front camera 46 can be positioned to theoutside in the left-right direction in comparison to when the left frontcamera 45 and the right front camera 46 are attached to the roof of thecab 6. As a result, images of the vicinity of the left lower edge of theblade 3 and the rotating conditions of the left crawler belt 10 a aswell as in front of the bulldozer 1 can be easily captured by the leftfront camera 45. Moreover, images in the vicinity of the right loweredge of the blade 3 and the rotating conditions of the right crawlerbelt 10 b as well as in front of the bulldozer 1 can be easily capturedby the right front camera 46. Therefore, the progress of work and thetraveling state can be easily understood from the images captured by theleft front camera 45 and the right front camera 46.

Although exemplary embodiments of the present invention have beendescribed so far, the present invention is not limited to the aboveexemplary embodiments and various modifications may be made within thescope of the invention.

The bulldozer 1 is not limited to a vehicle that is operated remotely.The bulldozer 1 may be operated with operating members disposed in thecab 6.

The number of cameras is not limited to four. The number of cameras maybe less than four or greater than four.

The left front camera 45 may be positioned further to the rear than theleft side camera 43. The right front camera 46 may be positioned furtherto the rear than the right side camera 44.

The left front camera 45 may overlap the left pillar portion 13 a asseen in the side view of the bulldozer 1. The right front camera 46 mayoverlap the right pillar portion 13 b as seen in the side view of thebulldozer 1. The left front camera 45 and the right front camera 46 maybe disposed at the same height as the beam portion 13 c.

The left front camera 45 may be positioned higher than the roof of thecab 6. The right front camera 46 may be positioned higher than the roofof the cab 6. In this case, the left front camera 45 is preferablypositioned so that images of the ground surface Ga between the blade 3and the left crawler belt 10 a can be captured as illustrated in FIG. 9for example. The right front camera 46 may be positioned in the sameway.

A control system for displaying the images of the cameras on the display34 may be provided in addition to the remote operating device 30. Asillustrated in FIG. 10 for example, a display controller 35 separatefrom the remote controller 32 may receive the image data captured by thecameras 41-46 via communication devices 36 and 37. The displaycontroller 35 may display the image data captured by the cameras 41-46on the display 34.

According to the present invention, the progress of work and thetraveling state can be easily understood with a camera attached to abulldozer.

What is claimed is:
 1. A bulldozer comprising: a vehicle body includinga cab; a blade disposed in front of the vehicle body; a left crawlerbelt disposed to the left of the vehicle body; a right crawler beltdisposed to the right of the vehicle body; a protective structureincluding a left pillar portion disposed to the left of the cab andextending in the up-down direction, a right pillar portion disposed tothe right of the cab and extending in the up-down direction, and a beamportion disposed above the cab and coupling the left pillar portion andthe right pillar portion; a first camera attached to the left pillarportion, a first optical axis of the first camera facing forward anddownward, the first camera overlapping the left crawler belt as seen ina plan view of the bulldozer and being arranged to capture a first imageof a gap between a lower edge of the blade and the left crawler belt; asecond camera attached to the right pillar portion, a second opticalaxis of the second camera facing forward and downward, the second cameraoverlapping the right crawler belt as seen in a plan view of thebulldozer and being arranged to capture a second image of a gap betweena lower edge of the blade and the right crawler belt; and a displayconfigured to display the first and second images side-by-side.
 2. Thebulldozer according to claim 1, wherein the first camera is disposedfurther to the left than the left pillar portion.
 3. The bulldozeraccording to claim 1, wherein the second camera is disposed further tothe right than the right pillar portion.
 4. The bulldozer according toclaim 1, wherein the first camera is disposed further to the front thanthe left pillar portion.
 5. The bulldozer according to claim 1, whereinthe second camera is disposed further to the front than the right pillarportion.
 6. The bulldozer according to claim 1, further comprising aleft hydraulic cylinder and a right hydraulic cylinder connected to thevehicle body and the blade, the first camera being disposed further tothe left than the left hydraulic cylinder.
 7. The bulldozer according toclaim 1, further comprising a left hydraulic cylinder and a righthydraulic cylinder connected to the vehicle body and the blade, thesecond camera being disposed further to the right than the righthydraulic cylinder.
 8. The bulldozer according to claim 1, wherein thefirst camera is disposed higher than a roof of the cab.
 9. The bulldozeraccording to claim 1, wherein the second camera is disposed higher thana roof of the cab.
 10. The bulldozer according to claim 1, furthercomprising a plurality of indicator lamps attached to the left pillarportion and disposed in the up-down direction.
 11. The bulldozeraccording to claim 10, wherein the first camera is disposed further tothe front than the plurality of indicator lamps.
 12. The bulldozeraccording to claim 1, further comprising a plurality of indicator lampsattached to the right pillar portion and disposed in the up-downdirection.
 13. The bulldozer according to claim 12, wherein the secondcamera is disposed further to the front than the plurality of indicatorlamps.
 14. The bulldozer according to claim 1, further comprising athird camera attached to the left pillar portion, a third optical axisof the third camera being inclined to the left and downward, and afourth camera attached to the right pillar portion, a fourth opticalaxis of the fourth camera being inclined to the right and downward. 15.The bulldozer according to claim 14, wherein the first camera isdisposed further to the front than the third camera; and the secondcamera is disposed further to the front than the fourth camera.
 16. Thebulldozer according to claim 14, wherein the first camera is disposed ata same height as the third camera; and the second camera is disposed ata same height as the fourth camera.
 17. A bulldozer body comprising: avehicle body including a cab and an engine compartment disposed in frontof the cab; a left crawler belt disposed to the left of the vehiclebody; a right crawler belt disposed to the right of the vehicle body; aprotective structure including a left pillar portion disposed to theleft of the cab and extending in the up-down direction, a right pillarportion disposed to the right of the cab and extending in the up-downdirection, and a beam portion disposed above the cab and coupling theleft pillar portion and the right pillar portion; a first cameraattached to the left pillar portion, a first optical axis of the firstcamera facing forward and downward, the first camera overlapping theleft crawler belt as seen in a plan view of the bulldozer and beingarranged to capture a first image of a gap between a lower edge of theblade and the left crawler belt; and a second camera attached to theright pillar portion, a second optical axis of the second camera facingforward and downward, the second camera overlapping the right crawlerbelt as seen in a plan view of the bulldozer and being arranged tocapture a second image of a gap between a lower edge of the blade andthe right crawler belt; and a display configured to display the firstand second images side-by-side.